Electrical searching-coil



A. R. COMSTOCK. ELECTRICAL SEARCHING COIL.

APPLlcATloN man 1AN.24. 1920.

Patented Dec. 27, 1921.

il; :2122121231131 2..;122-'I` UNITED STATES ARCI-IIE R. COMSTOCK, OFMOUNT KISCO, NEW YORK.

ELECTRICAL SEARCHING-COIL.

Lacasse.

Specification of Letters Patent.

Patented Dec. 27, 1921.

Application filed January 24, 1820. Serial No. 353,872.

To all w from t may-concern Be it known that I, Anonm It. CorrsToC-ii, acitizen of the United States, residing at Mount Kisco, in the county oflVestchester.

tate of New York7 have invented certain new and useful Improvements inElectrical Searching-Coils; and I do hereby declare the following to bea full7 clear, and exact description of the invention, such as willenable others skilled in the art to which itappertains to make and usethe same.

This invention relates to electrical coils and particularly toelectrical searching coils which may be utilized to locate trouble suchas short-circuits or grounds in wire communication systems, for example7telephone lines, by means of inductive or other similar electricalphenomena.

Heretofore the approximate location of grounds and short-circuits intelephone or telegraph lines has been accomplished by means of theso-called Wheatstone bridge methods which are generally familiar. Thesemethods are only approximate and require the lineman to travel from poleto pole within a certain area, in order to detect the ground orshort-circuit. Frequently the approximation made in the local test roomis not accurate and requires the lineman or repairman to make anextended search along the line in order to properly locate the troubleand repair the system so that it may be again utilized.

In accordance with this invention, substantially no approximations as tothe location of a short-circuit or ground are necessary and therepairman or lineman may immediately proceed on foot or in a vehiclealong a road which parallels the wire system, keeping within a distanceof approximately fifty feet of the line until the ground orshort-circuit is located by means of the searching coil. In this way itwill be seen that by the use of the improved searching coil, atelephone, telegraph or other line which 'is supplied with an audiblefrequency alternating current may be followed with accuracy until apoint is reached where the line is either grounded or short-circuited,thereby forming a. return path for the audible frequency currents.

The searching coil comprises a metallic core, a. primary winding of finewire electrically connected to the core, and a secondary windingconnected to the core and wound preferably at ight angles to the primarywinding. A telephone receiver may be directly connected to the free endsofvthe primary an'd secondary winding for the purpose of translating theaudible frequency currents induced` or set up in the searching coil. orany convenient amplifying means may be inserted between the searchingcoil and the telephone receivers for the purpose of amplifying theinduced or other currents set up within the coil in order that the coilmay be ut-ilized at greater distances from the line or system or forother reasons as required by the lineman or repairman.

The invent-ion will be more clearly understood from the accompanying'drawings which illustrate an embodiment of the iii-j vention. In thesedrawings:

Figure l illustrates the method of utilizing the searching coil for thepurposes of locating a short-circuit or ground in a telephone ortelegraph system;

Fig. 2 illustrates diagrammatically the arrangement of the primar',7windings upon the core of the searching coil;

Fig. 3 illustrates-a'convenient form of the searching coil for thepurpose outlined in connect-ion with Fig. l;

Fig. 4 is a cross sectional view of the searching coil taken along 4 4of Fig. 3; and

Fig. 5 is a` sectional view taken alongof Fig. 8.

Referring now to Fig. l, and assuming that the wires l and 2 have beensupplied with audible frequency electrical oscillations at the centralstation, the lineman or repairman looking for the trouble in this systemwould follow the line carried by poles such as 3 and et, either on foot,or in a vehicle if the line parallels a road, and would keep a telephonereceiver or receivers 5 connected to the searching coil 69 in anoperative position over his ears. If the repairman or lineman followsthe line and keeps well within the field set up by the electricaloscillations carried by the line, an audible tone will be heard in thetelephone receivers 5 as a result of the currents induced or set up vinthe searching coil 6. This audible note will continue up to the point 7,beyond which there will be no response in the telephone receiver. It isto be understood that the distance to which a repairman may work from aline and secondary iio may be increased bythe use of audible frequencycurrent amplifying means and by the use of sensitive telephonereceivers.

In Fig. 2, which illustrates the preferred embodiment of the searchingcoil, a core 8 of electrically conductive material is shown, upon whicha primary Winding 9 of ne Wire is electrically connected to the core 8at one end of the Winding, shown at the point 10. The secondary Winding11 of the coil is also electrically connected to the core S at the point12 and is Wound about the primary winding 9 at right angles thereto. Thefree ends of the primary and secondary Winding are shown at 13 and 141,respectively.

It has been found by experiment that a core of silver is preferable butcores of other electrically conductive metals such as copper or softiron may be used. It has also been found that superior results areobtained when the secondary Winding of coarse wire is Wound at rightangles to the primary Winding. The Wire forming the secondary Windingmay be twice the diameter of the Wire forming the primary winding andgood results have been obtained from a searching coil in which the ratioof primary turns to secondary turns is one hundred to one.

In Fig. 3 a completed searching coil 6 is shown which is suitable forplacing in the pocket of a repairman or lineman and Which may beutilized in conjunction With sensitive telephone receivers to Work at adistance not greater than fifty feet from the telephone line whichcarries the audible frequency alternating currents. The free ends 13 and1a of the primary and secondary windings of the searching coil areconnected respectively to the binding poss 15 and 16 and which are inturn connected directly to the telephone receivers, or to the telephonereceivers throu h suitable amplifying apparatus.

In` ig. 4 the arrangement of the searching coil 6 is shown within itsmoisture-proof lcasing 17 which entirely surrounds the coil and preventsthe entrance of any liquid. This coating may be of Celluloid, rubber orother material having suitable insulating and moisture-proof properties.

In Fig. 5 the primary Winding 9 and the secondar f Winding 11 are shown`in their respective relations to the core 8; the casing 17 retainingthe windings and core in a permanent position with respect to oneanother.

It is to be understood that while I have shown and described but oneembodiment of this invention, that numerous modifications andarrangements of core, primary Winding and secondary Winding may be madeWithout departing from the spirit and scope of this invention.

-I claim 1. An electrical searching coil comprisingl a core ofelectrically conductive material, a primary Winding electricallyconnected thereto and Wound thereon, a secondary Winding electricallyconnected to said core and Wound thereon in an angular relation to saidprimary Winding.

'2. An electrical searching coil comprising a metallic core of highVelectrical conductivity, a primary Winding Wound thereon andelectrically connected thereto, a secondary Winding electricallyconnected to said core and Wound upon said primary Windingat rightangles thereto. V

3. An electrical seaching coil comprising a core of silver, a primaryWinding of iine Wire electrically connected thereto at one end of theLsaid Winding and Wound thereon, a secondary Winding of'coarser Wireelectrif cally connected to said core at one end of said Winding andWound uponsaid primary Winding at right angles thereto. Y

In testimony whereof I aix my` signature.

ARCI-IIE R. COMSTOCK. i

